Large-signal stability analysis of islanded DC microgrids with multiple types of loads.

• The large signal stability of DC microgrid with integrated load is analyzed. • Stability conditions of DC microgrid are derived by Lyapunov direct method. • Load power limits under stability constraints and voltage constraints are given. • Stability limit of CPL is affected by resistive load and system parameters. • Conclusion is helpful to the load management and planning of DC microgrid. Due to the lack of support for the power system, the small inertia of the system, and the access to negative impedance elements, the stable operation of the islanded DC microgrid can be challenging. To ensure the stability of the system in a large operating range, a system-level large-signal stability analysis is carried out for a droop-controlled dc microgrid in this article. Firstly, the system-level equivalent model of the DC microgrid is established, the steady-state of the DC microgrid is analyzed and the instabilities principle, as well as their physical interpretation, is revealed. Second, necessary and sufficient conditions of the DC microgrid are deduced by the Lyapunov direct method, and the load limit of the DC microgrid is obtained under the restriction of stability and voltage deviation. Third, the correctness of the theoretical analysis is verified by the simulation results of a droop-controlled DC microgrid system. [ABSTRACT FROM AUTHOR]